engleski

Single acute stress-induced progesterone and ovariectomy alter cardiomyocyte contractile function in female rats

To assess how ovarian-derived sex hormones (in par ticular progesterone) modify the effects of ingle acute stress on the mechanical and biochemical properties of left ventricular cardiomyocytes in the rat. Non-ovariectomized (control, n=8) and ovariectomized (OVX, n=8) female rats were kept under normal conditions or were exposed to stress (control-S, n=8 and OVX-S, n=8). Serum progesterone levels were measured using a chemiluminescent immunoassay. Left ventricular myocardial samples were used for isometric force measurements and protein analysis. Ca2+ dependent active force (F active), Ca2+ independent passive force (F passive), and Ca 2+ sensitivity of force production were determined in single, mechanically isolated, permeabilized cardiomyocytes. Stress and ovariectomy induced alterations in myofilament proteins (myosin- binding protein C [MyBP-C], troponin I [TnI], and titin) were analyzed by sodium dodecyl sulfate gel electrophoresis using protein and phosphoprotein stainings. Serum progesterone levels were significantly in creased in stressed rats (control-S, 35.6±4.8 ng/mL and OVX-S, 21.9 ±4.0 ng/mL) compared to control (10±2.9 ng/mL) and OVX (2.8±0.5 ng/mL) groups. F active was higher in the OVX groups (OVX, 25.9±3.4 kN/m 2 and OVX-S, 26.3±3.0 kN/m2) than in control groups (control, 16.4±1.2 kN/m2 and control-S, 14.4±0.9 kN/m2). Regarding the potential molecular mechanisms, F active correlated with MyBP-C phosphorylation, while myofilament Ca2+ sensitivity inversely correlated with serum progesterone levels when the mean values were plotted for all animal groups. F passive was unaffected by any treatment.Conclusion Stress increases ovary- independent synthesis and release of progesterone, which may regulate Ca 2+ sensitivity of force production in left ventricular cardiomyocytes. Stress and female hormones differently alter Ca2+ dependent cardiomyocyte contractile force production, which may have pathophysiological importance during stress conditions affecting postmenopausal women

Acute stress; ovariectomy; progesteron; cardiomyocytes; left ventriculi; rat

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